Concentration of ores by flotation



Patented 0d. 21, 1924.

RALZPH E. SAYRE, OF NEW ROCHELLE, NEW YORK.

GONCENTRATl [ON OF ORES BY FL'DTATION.

No Drawing.

To all whom it may concern:

, Be'it known that I, RALPH E. SAYRE, a citizen of the United States,residing at New Rochelle, in the county of Westchester, State of NewYork, have invented certain new and useful Improvements in theConcentration of Ores by Flotation; and I do hereby declare thefollowing to be a full, clear, and exact description of the invention,such as will enableothers skilled in the art to which it appertains tomake and use these-me.

This invention relates to the concentration of ores, minerals and thelike by flotation and has for its object the provision of certainimprovements in flotation processes.

The invention is based upon the discovery that improved results areobtained by carrying out the flotationoperation in a non-acid oralkaline pulp in the presence of a heavy metal xanthate, that is a heavymetal salt of xanthic acid. 1 have found that heavy metal xanthates, andmore particularly lead xanthate, are admirable flotation agents in anon-acid or alkaline pulp. Such Xanthates have a marked selective actionon sulfide minerals, as distlngmshed. from gangue minerals, and causethe sulfide minerals to float 1 readily with an attendant high recoveryof the metal values. My investigations have indicated that theXanthates, in a non-acid or alkaline pulp, are lacking in frothingpower, so that an appropriate frothing agent, such as pine oil orterpineol should be employed in conjunction therewith in carry ing outthe flotation operation.

The heavy metal Xanthates are solid compounds, and in general are onlyslightly soluble in water. A heavy metal xanthate may be obtained byadding a solution of a heavy metal salt to a dissolved Xa-nthate, suchfor example, as potassium or sodium xanthate. In most cases,precipitation of the desired xanthate occurs immediately,

and if the conditions are favorable, the yield is practicallyquantitative as calculated on the amount of potassium xanthate used.

Being the salt of a weak acid, the heavy metal xanthate may be easilyhydrolyzed, and even very dilute mineral acids liberate xanthic acidfrom it.

Free xanthic acid is an oily liquid, heavier than water, in which it isvery slightly soluble and possesses a strong disagreeable odor. Xanthicacid is quite unstable, breaking up spontaneously into carbon bisulfide'and Application filed November 24,1923. Serial No. 676,859.

alcohol. Authoritative reference books give 249 C. as the temperatureat' which such. decomposition occurs, but my investigations haveindicated that xanthic acid decomposes into carbon bisulfide and alcoholat even lower temperatures.

While xanthic acid appears to have some selective action or collectingpower for sultide minerals in the flotation operation, it is in no senseso powerful and satisfactory a flotation agent as the xanthates.Furthermore, owing to the instability of xanthic acid it is eflectiveonly at low temperatures, or when the flotation operation is performedimmediately after its introduction into or liberation in the ore pulp.Otherwise decomposition of the Xanthic acid takes place and nobeneficial effect in the flotation'operation is obtained.

My investigations have demonstrated that the beneficial effects of thexanthates as flotation agents are secured only in non-acid or alkalinemineral pulps. When a heavy metal xanthate, such for example as lead orzinc xanthate, is added to an acid mineral pulp, xanthic acid isliberated. If the tem- Jerature of the pulp is much above 10 C. theliberated Xanthic acid is soon decomposed into carbon bisulfide andalcohol. F or these reasons, my investigations have indicated that theuse of Xanthates in an acid pulp give very erratic, unreliable andunsatisfactory flotation results.

Vl'hen the Xanthate, such as lead Xanthate, zinc .xanthate, or the like,is used as a flotation agent in a neutral (that is non-acid) or alkalinepulp, very satisfactory flotation results are secured. Where the ore ormineral pulp is normally acid, any appropriate alkali may be used tomake the pulp neutral or alkaline. In this connection, satisfactoryresults are obtained with such alkaline agents as caustic soda, sodaash,or lime. It is preferable in general practice to add the alkaline agentto the ore or mineral prior to the line grinding which usually precedesthefiotation operation. It is generally preferable to add the heavymetal xa-nthates to theflotation circuit prior to the final grinding ofthe ore or mineral.

'Lhave found that while the heavy metal Xanthate brings about a highrecovery, using either lime or caustic soda in the proportions of fourpounds per ton of dry ore, the use of lime is generally preferable. Thisseems to be due to, an inhibiting action on the froth when caustic sodais used, in consequence of which from 3 to 6 times the usual amount offrothing' a With lime, on the other quantity of frothin agent suflices.The flotation resu ts secured, when using heavy metal xanthates asflotation agents, vary with the xanthate used. I have secured ton of dryore or even less,

heavy metal xanthates on ore-of the Utah Uopper Company assaying 1.20%copper. In each case, 500 grams of minus mesh ore was ground for'20minutes in a-pebble mill with 250 c. c. of water towhich lime and v theiranthate in the proportion of four pounds and 0.2 pounds respectively,per ton "of ore, had' been added; The resulting pulp 25 was diluted toabout 2 I terpineol was added and flotation was performed 1n. a Callowrou gher cell.

nt is' required t 1 m most satisfactory results with leadxan'thate;

Flotation tests have shown that good re 4 sults can obtained when thesecompounds are used in the proportion of 0.1 pound per The followingtable gives some typical flotation results obtained with a numberofliters, a drop of of minerals by flotation which comprises subjectingthe mineral in the form of an alkaline pulp to a flotation operation inthe presence of a heavy metal xanthate. v V

3. The improvement in; the concentration of minerals by flotation whichcomprises subjecting the mineral in the form of a pulp made alkaline bythe addition of lime to a flotation operation in the presence of a heavymetal .xanthate.

4. The improvement in the concentration of minerals by flotation whichcomprises subjecting the mineral in the form of a nonacid pulp to aflotation operation inzthe presence of lead xanthate.

5. The improvement in the concentration of minerals by flotation whichcomprises subjecting the mineral in the form of an alkaline pulp to aflotation operation in the pres ence of lead'xanthate. e

6. The improvement in the concentration .of minerals byflotation whichcomprises sub'ectingthe'mineral in the form of a pulp made alkaline bythe addition of lime to a flotation operation in the presence of leadxanthate. i

a 7. The improvement in the concentration Tailing Reco cry 3 7 01] 4 Iclaim 1. The improvement in the concentration of minerals by sub'ectingthe aci pnlp toa ence of a heavy metal xanthate.

2. The improvement in the concentration flotation which comprisesglimeral in the form oi a nontation operation in the pres-' of mineralsby flotation which comprises subgetmg the mineral in the formof a nonacipulp to a flotation operation in the presence of a-heavy metal xanthateand a frothing a fielnt. 8. e improvement in the concentration ofminerals by flotation which comprises subjecting the mineral in the'formof an alkaline pulp to aflotationoperation in the presence of leadxanthate anda frothing agent. 1

9. Theimprovement in the concentration of minerals byflotation" whichcomprises subjecting the mineral in the form of a pulp made alkaline bythe addition of lime to a flotation operation in the presence *of leadxanthate. .t f In testimony'whereof I aflix my si ature. RALPH E. SA E.

